Treatment planning and biomechanics of distraction osteogenesis from an orthodontic perspective.

As in traditional combined surgical and orthodontic procedures, the orthodontist has a role in the planning and orthodontic support of patients undergoing distraction osteogenesis. This role includes predistraction assessment of the craniofacial skeleton and occlusal function in addition to planning both the predistraction and postdistraction orthodontic care. Based on careful clinical evaluation, dental study models, photographic analysis, cephalometric evaluation, and evaluation of three-dimensional computed tomographic scans, the orthodontist, in collaboration with the surgeon, plans distraction device placement and the predicted vectors of distraction. Both surgeon and orthodontist closely monitor the patient during the active distraction phase, using intermaxillary elastic traction, sometimes combined with guide planes, bite plates, and stabilization arches, to mold the newly formed bone (regenerate) while optimizing the developing occlusion. Postdistraction change caused by relapse is minimal. Growth after mandibular distraction is variable and appears to be dependent on the genetic program of the native bone and the surrounding soft tissue matrix. A significant advantage of distraction osteogenesis is the gradual lengthening of the soft tissues and surrounding functional spaces. Distraction osteogenesis can be applied at an earlier age than traditional orthognathic surgery because the technique is relatively simple and bone grafts are not required for augmentation of the hypoplastic craniofacial skeleton. In this new technique, the surgeon and the orthodontist have become collaborators in a process that gradually alters the magnitude and direction of craniofacial growth.